There is currently a growing demand for engine materials and/or components which offer greater wear resistance and reduced friction. With respect to the automotive sector, and more specifically the lining and/or treatment of surfaces of combustion engine cylinders/bores, recent research has been developed with a view to obtaining surface materials and finishes which contribute to a reduction in fuel consumption, and consequently CO2 emissions, through reduced losses due to friction. Solutions involving nanotechnology have been the particular focus of recent research.
A possible solution is described in the patent document EP 2 229 467 which describes a method for manufacturing a mechanical element, such as an engine component, which has a surface of reduced friction which has a tribochemical conditioning/deposition of a substance such as a solid lubricant, which covers the surface of the element.
Patent document CA 2 704 078 is very similar to the above European document and relates to the process for manufacturing a low friction element by tribochemically conditioning a solid lubricant, specifying the application of the solid lubricant to an engine cylinder liner.
Finally, patent document US 2010/0272942, of the same family of both of the above-mentioned documents, relates to a similar manufacturing process, with the emphasis on its use in cylinder liners and engine block cylinders.
The three patent documents mentioned relate to a dedicated metal mechanical process which combines the extreme mechanical pressure of honing the surface of the component with the tribochemical or mechanicochemical deposition of the anti-wear film of low friction tungsten disulphate (WS2).
Despite the advantages of reducing friction and wear in liners/cylinder, the extreme pressure applied during the tribomechanical conditioning used in the above-mentioned technique, may deform the liner/cylinder from its ideal circular shape in the thin-walled blocks normally used in low weight engine blocks. To prevent the increase in the consumption of lubricating oil in the aforementioned bore/cylinder of deformed engine blocks, use must be made of piston rings with higher forces, which jeopardises the reduction in friction.
With a view to minimising the above-mentioned reduction in friction when piston rings with a higher load is used, the original roughness of the bore/cylinder of the blocks may be reduced, which may not be desirable. This is due to the fact that some degree of roughness is desirable since the roughness may serve as a lubricating oil reservoir, thus enabling the parts, the piston rig and block bore/cylinder, soften in the first few hours of operation of the engine.
For the purpose of overcoming such limitations, the inventors have developed an improved tribomechanical conditioning process by using low pressure during the honing process yet still achieving a significant reduction in friction according to the description below.